How to tell if game is running in fullscreen and borderless window

If I have a particular game that is taking up my entire screen, what ways are there to figure out whether that game is running in Fullscreen or Borderless Windowed mode?

The obvious solution for most games is to check what the graphics options say. One problem I've seen with this advice though is that I've heard of some games (can't think of any specific examples) where it's "Fullscreen" option actually runs the game in a Borderless Window.

Solution 1:

If you ALT+TAB out of the game and the game minimizes, then its fullscreen (requires another application window in the background). If it stays open, then its borderless window.

To add to the paragraph above: If you don't have any other application window in the background, then simply open the taskmanager via CTRL+ALT+DEL and see if the game minimizes (another option is WIN+R to open the Run window).

Also if you have a second monitor, you will only be able to access it without ALT+TAB when the game is in borderless window. While the game is in fullscreen your mouse is locked to that specific screen.

Another option which I am currently not entirely sure about is the WIN key. If you hit it, the start menu opens up and should minimize fullscreen games, while borderless window games stay open